Patch testing is a common diagnostic tool used to identify the specific substances that trigger contact dermatitis reactions. Contact dermatitis is a localized irritation of the skin in response to a certain substance that is otherwise harmless. Common trigger substances include poison ivy, jewelry, hair care products, cleaning solution, detergent, cosmetics, perfumes, and latex rubber.
With allergic contact dermatitis, typically harmless substances cause an immune system reaction when they come in contact with the skin. The reaction to trigger substances causes localized symptoms about one to two days after exposure but sometimes as late as 1 week after exposure. These symptoms may include:
These symptoms can last for up to four weeks, and can usually be treated at home through medications and topical creams. The best protection against contact dermatitis is to identify the specific triggers through this allergy skin patch test. Patients can then avoid these substances as often as possible.
Although allergic contact dermatitis is similar to other allergies in that it triggers an immune system response, these triggers are external rather than internal. Thus, patch testing is also done externally and does not require the use of any needles or injections.